Condenser and process



Mllch E5, R932. W; M PRESS dug coNDENsER AND vPROCESS Original FiledApril 30. 1920 www@ mentioned.

atented Mar id; i932- @ne ci the rst steps in the process ofinakingcondensers consists in assembling alter nate sheets of conductingand dieiectric niateriais to huiid up a condenser stack of the requiredheight, these sheets oi materialA heing separated hy insulation havingsuitable properties tor this peculiar class of Work. Notwithstandinggreat cere in selecting these materials and in aernhiing them', it is avery common experience to have a condenser break down during test orwhiie in use' and it has been deniteiy' determined that a veryirnportant cause of such breakdowns is the pres,

ence or voids, gas, or an excessive amount o insulating material betweenthe sheets of inaterial that maire up the condenser. i

it is an important object oi the present invention to devise a processof making condensers which will reduce to a minimum imperfections andfaults of the character above in other Words, the invention aims todevise a process of huiiding condensers which will eiiininate anunnecessary thickness of insulating; material ToetWeen the layers ofconducting and dielectric materials that maire up the condenser andwhich will also reduce to a minimum the presence of voids, hiisters orbubhies in the condenser. it is also an` object of the invention todevise a process oi making condensers Which rvili produce a condenserthat is a firm mechanical mass, that will have a very low dielectricloss and in which the leakage between successive conducting; elements ofthe condenser Willbe reduced to a minimum. A further object of theinvention is to improve condenser constructions hot-h from an eiectricaiand also from a mechanical standpoint.

This appiication is a division of my copending appication lSerial No.377,977, iiled April 30, i920, which has eventuated into Patent No.1,721,503, dated July 23, 1929.

The invention also consists in certain new and original features ofconstruction and CT EL'NTCLAIR,

CGE-@ELLE I GGBEQRATEGH NEW Biv'd and this application le rovembercombinations of parts hereinafter set forth and claimed.

ilthough the nove/l ies-,tures which are he iieved to characteristic ofthis invention will be particularly pointed out in the claims appendedhereto, the invention itseii, as to its objects and advantages, the modeci its operation andthe manner of its organization may he betterunderstood hy referring to the following. description with theaccompanying part thereof, in which Fig. l is a front elevation showingin the process of manufacturing o a condenser constructed in accordancewith the in vention and the apparatus used therefor;

Figs. 2 and 3 are side and vplan views Vo: the apparatus-shown in Figi;and

Figs. land 5 are pien and side views respectivey of the iinishedcondenser.

Like reference characters denote like parts in the several figures ofthe drawings. i

in the oiiovving description and in the ciaims parte will he identifiedby speciic names for convenience5 Tout they are intended to he asgeneric in their application to similar parts as the art vviil, permit.

ssuining that fthe mica or other dielectric elements to he used in thecondenser have been made hy splitting the mica sheets to the desiredthickness and cutting them out to the required shape and dimensions, andalso that the tin foil or other conducting elements of suitable shapeand size have been provided the next step is to coat'the mica elementsWithvarnish or other adhesive insulating material. is desirable thatthis coating shall be very thin and that it shall completely cover bothsurfaces of each mica sheet. This coating' operation may he performed inany suitahie manner and with any suitahle insulating material, such forexarnpie as varnish.

After the dielectric elements have been coa-ted and partially dried,they are next rauen lin connection drawlngs 'forming a assembled withsheets of tin foil, or other conducting material of the proper size andshape, to form a condenser stack. The condenser stack may either bebuilt up in the form of a tall stack that later is split up into unitsof the required height, or the stack may be built up in the form ofindividual units, each unit stack being kept separate from the others.

After the assembly of the stack has been completed, the stack is nextheated or baked for the purpose of driving out the solvent in thevarnish, eliminating any excess of var-l nish between the elements,and-driving out any gas'or vapor that may be pocketed between theelements of the stack. A further result accomplished in the bakingoperation when certain varnishes are used is the oxidizing or chemicalchanging of the solid opnstituents of the varnish.

For this purpose the condenser stack preferably is transferred to abaking stand of the general character illustrated in Figs. 12 and 3.

Assuming that the condenser stack has been assembled in units, as abovedescribed, these units are placed one above the other in a stand whichcomprises a base 16 and two posts 17 and 18 rising from the oppositesides oit the base and threaded near their upper ends. The individualunits are separated from each other by separator strips 19 of brassl orother suitable material having holes drilled in them so that they slidefreely on the posts 17 and 18.

Each unit is located between two metallic spring plates normallyconvenly curved or bowed with reference to the condenser, as

' clearly' shown in Fig. 2, one of these plates being designated at 50andthe other at 51. lt will be seen that the plates are alike inconstruction and that each plate is provided at opposite ends withprojections extending at substantially right angles to the plate anddesigned to lit over the opposite sides or edges of 'the condenser unit.Ears 52 and 53 also project on these plates and have holes punched inthem. The parts 50 and 51 consist preferably of a metal which can beeasily bent or shaped to form the intermediate spring portions and therigid angular projections. Any suitable sheet metal is adapted for thispurpose, such as steel or phosphor bronze. ln assembling the parts 50and 51, the spring portions are arranged I on opposite sides of thestack with their convex surfaces facing the same and in, parallelismwith the sheets composing the stack.' rlhe are then compressed flatagainst the stack and rigidly secured at opposite sides as hereinafter.described to maintain lthe sheets together under spring compression.

The clamp comprises two parts which lcan be cheaply' made and easilyassembled to maintain the stack under good compression Lacasse and atthe same time allow the leads to be brought out at opposite ends of thestack,-` the stack projecting at opposite ends beyond sure plate 22 atits lower end and threaded through a yoke or plate 55 which is removablysecured to the upper ends ot' the rods 17 and 18,. The handle 56 issecured to this screw and allords a convenient means for `turning it. Itwill be seen that with this arrangement the entire stack can becompressed until the springs 50 and 51 are straightened out, thuscompressing the units with a spring pressure. The baking stand with thestack lof condenser units clamped therein is then placed in an oven andbaked for several hnurs at a temperature oiapproximately 110 to 115o C.

While tbe greater part of the solvent in the varnish coating of thedielectric elements is eliminated before these elementsV are assembledto form acondenser stack, a certain amount of solvent still remains inthe lower layers of the varnish coating Furthermore, the coating isthicker than is necessary. The baking of the stack while it ismaintained. under a heavy spring pressure squeezes out the surplusvarnish which softens under the relatively high degree of heat to whichit is subjected. At the same time this comparatively high heat vaporizesthe solvent together with any other vaporizable elements, such for"instance as traces of water5 which may be pocketed between the Sheets,and the heat, together with the pressure, c'o-operate to reduce to aminimum gas, vapor, and the thickness of the adhesive remaining betweenthe sheets. ln other words, theheat tends to diluse any gases orvaporizable materials present between the sheets while the pressuretends `to squeeze out these materials from between the sheets of thestack. When separator plates 19 made of brass or similar material areused,as distinguished from insulating material, they serve not only toseparate the units and give the stack additional mechanical ri idity,but alsoto conduct yheat into the interior of the stack and thus tofacilitate the baking operation.A The oven is lUU lla)

ventilated during the baking operation for the purpose of carrying oil'the solvent vapors and also, when an oxidizable varnish such i as copalvarnish 1s used, to provide an ample supply of oxygen to eect thisoxidation.

lil.

described elimination of the greater part o:A

tbe solvent from the varnislicoeting on the dielectric elements beforethese elements are assembled to forni e condenser stack. This leavesonly enough solvent in the coating to cause the coating to softenbecorne sticky during tbe baking operntion, which result is desirable etthis tirnelor the purpose of adbesively securingv eil 'the sheets ofmateriel firmly together, and since only e relatively small quantity ofsolvent still remsins in the costing, the eliniinstion or thesolvent canbe made rnucli more. complete by the bulging;

step would otherwise be practicable. further udvun'tageous resultproduced by this process is tbe sealing; of lthe marginal spaces betweenadjacent dielectric elements of the stack. Esch conducting element lyingon e mica sheet is surrounded on three sides by en inactive` or@ rnics;that is, nn ares. of mice that is not subjected to tile dielectricstrain. This margin covered with varnislil during the costing operation,es above described7 end the compression to which tlie condenser steclrisnot subjected to tbe dielectric strain. liis margin is covered 'withvarnish during the costing operetion, es -ebove described, end thecompression to which the condenser stack is subgected during the bal--ing operation results in squeezing additional varnish out from betweenthe overlapping sheet and into these rnnrginal spaces.

rl'his varnisl'i completely se'sls tbe space between the inactivemargins of adjacent dielectric elements. lt vvill be understood thatwhen a condenser is in -use there is n ndency for the current to.discharge. from the edge of one of the conducting elements ecross theinactive margin to the edge of the next adja- .cent conducting element.rdinarily, e comparatively free patin is left ortbis dis charge over thesurface of the mica. The sealing ol these marginal spaces, however, byvarnish introduces s solid wall of insulating material in the path ofthis discharge and thus reduces very substantially tbe surface leakagethat otliervvise would be present in the condenser. In other Words, thisconstrue tion reduces the electrical loss in the condenser.

After the locking operation has been cornm pleted, tlie condenser willbe found to be ek firm, mechanical mass capable ol withstanding 'veryrough usage. The sealing of tlie edges, as above described, contributesto this result and also is of advantage when the condenser is to be usedin a deinp location.

After the condenser has been baked its manufacture muy be completed inany desired manner. According to the process which l prefer et present,the condenser units are next tested end any units which fail towithstand tlie tests are discarded. lln order to reduce still :furtherthe electrical losses in the condenser and else vfor the purpose ofimproving its mechanical structure, it is preierable under sonneconditions to repeat the bebng operation.

rEllis second bulging need not be continued sslono es the first butusually is from sinl to eight nours et s temperature from il() degreesto 115 degrees C. The exact nature of the change produced in thecondenser by this second baiting is dicult to determine but probably isdue to scene change produce-d in the exceedingly thin lilm of vsrnislithat still remains between the sdjecent elements of the condenser.lieve. detrrnined, however, by actual test tiiat the electricalcharacteristics o? tbe condenser are improved by tliis second l bakingand that they can be still further lmproved by e tliird or ourtli 'lCliedegree of improvement, liovvever, decreases with successive belringsusually it is not advisable from u manufacturing standpoint 'curry diecondenser through more tiren two or these lient cycles.

.The or beting, end il desiredelso, tile relieating or subsequent bakingoperations ere performed in tbe-manner ebove described, but after tbelocking operation tias been coinpleted the projecting ends oit tbespring plates which lis-ve ncrv been brought' into overlappingrelationship et opposite sides of each unit, are permanently securedtogether by soldering or Welding. Preferably this securing operntion isperfor ed by spot vvelding, as indicated at 5'?, lig. 5. Tae condenserterminals 58, 59 are sliovvn in, l und 5 connected to tile `foil sheetsprojecting 'lroni the stack. As shown in Fig. fl the integral parte 52,53 ere formed with holes fior securing the finished condenser in piece.

This process results in enclosing tbe condenser staclr in e casing whichbecause of its resilient nature and tbe manner in which it is secured onthe steclr, exerts a permanent spring pressure on the stack oversubstantially its entire active areas. After the securing operation theunits may be removed from the baking stand.

rlbe connections tothe op 'te sets of conducting elenients can bemadigsiln any convenient'inanner es, for instance, by soldering leedsl58 und 59 to these conducting elements respectively, with a suitablesoft solder. The punched ears 52 and 53 are provided to facilitete thesecuring of the cornpletedcondenser lll@ to its support. rlhisconstruction provides a very compact and ecient condenser especiallyadapted for locations where the condenser is subjected to rough usage.

While certain novel features of the invention have been shown anddescribed andare pointed out in the annexed claims, it will beunderstood that various omissions, substitutions and changes in the'forms and details of the device illustratedand in its operation may bemade by those skilled in the art without departing from the spirit ofthe inven tion.

What is claimed is:

1. A sheet condenser which consists of a stack of interleaved liatsheets of mica and metal foils, the foils of opposite potential eX-tending out from spaced-apart portions of the side of the stack; and atwo-part metal clamp, the two parts of which extend. tlat oversubstantially the entire surfaces of the two faces of the stack; one ofsaid clamp-parts tending to assume a convexly curved shape Withreference to the stack-face which it engages and said part-s havingportions extending over portions of the side of the stack other thanthose from which the foils extend, to overlap one another; and saidoverlapped portions being permanently secured together While said convexpart lies substantially flat against thestack, whereby the stack is heldunder permanent spring compression.

2. The combination with an electrical condenser stack of Amica and foilsheets, of two metal plates holding the stack between them in thedirection of its height, and means for holding the stack under pressurebetween said plates; at least one of said plates being con- 'structed totend to assume a convexly curved shape and having its bowed portionarranged to bear against an end of the stack, said plate beingsubstantially straightened under said pressure.

ln an electrical condenser, a stack of condenser elements and a clampfor said stack comprising members engaging opposite sides of the stack,at least one of said members having integral lateral portions connectedto the other member, at least one of said members Ahaving a springyportion parallel with said elements whereby the elements are heldtogether under spring compression.

4. ln an electrical condenser, a stackof condenser elements and U-shapedspring clamping members having intermediate portions engaging oppositesides of the stack and connected together, holding the members againstthe stack to compress the elements together under spring pressure.

5. In an electrical condenser, a stack comprising alternate sheets ofconductor 4wand dielectric and a multi-part open ended sheet metal clampfor the vstack and comprising metal plates upon opposite .sides of thestack and integral lateral overlapping portions se curing the partstogether in clamping relation against -the stack.

6. In an electrical condenser, a iiat faced stack comprising alternatelat sheets of conductor and dielectric and a multi-part metal clamp forthe stack and comprising plates lying flat upon and extending oversubstantially the entire surface of nthe opposite dat faces of the stackand having integral portions extending at angle with the plates andalong the sides of the stack and connecting the parts together inpermanent clamping relation against the stack.

7. in an electrical condenser, a stack comprising alternate sheets'ofconductor and dielectric and a multi-part metal clampv for the stack andcomprising spring plates engaging opposite sides of the stack and havingintegral rigid lateral portions overlapping each other and securing theparts together in clamping relation against the stack under springpressure.

8. ln an electrical condenser, a stack comprising alternate sheets ofconductor and dielectric and a sheet metal clamp for the stack andcomprising plates engaging oppositel faces of the stack and angularlyarranged integral lateral portions bent to connect the plates togetherin clamping relation against the stack, at least one of said platesbeing a. spring and adapted to assume a concave-con'- vex shapewhen/released.

9. ln an electrical condenser, a stack comprising sheets .of lconductorand dielectric and metal spring plates upon opposite Asides of the stackand connected together along opposite edges of the stack transversely ofthe sheets to hold the sheets in contact under spring pressure.`

10. ln an electrical condenser, a. stack comprising sheets of conductorand dielectric and a clamp for said stack comprising spring members uponopposite sides of the stack and means connecting them and extendingalong opposite edges of the 'stack and trans- M0 versely of the edges ofthe sheetsfor maintaining said Vmembers in clampingrelation against thestack holding the sheets togethen underuspring pressure.

11. In an electrical condenser, a stack comprising alternate sheets ofconductor and dielectric and a sheet metal clamp for the stackcomprising parts at opposite faces of the stack, at least one of whichis springy, and integral rigid lateral portions bent to extend alongopposite edges of the stack and connecting the parts together inclamping relation against the. stack, holding the latter under springpressure.

l2. ln an electrical condenser, a stack comprising alterna-te sheets ofconductor and dielectric and sheet metal spring plates engaging oppositesides o-said stack, at least one of said plates having integral lateralportions bent to extend along opposite edges of the Leccese stack toconnecty the plates together, clamping the stack under spring pressure,said plates being formed` to assume a concavo-convex shape when releasedwith the convex sides facing the stack.

13. An electrical condenser comprising a stack of dielectric andarmature material, a. metal end member for said stack having portionsadapted to extend along opposite sides of said stack, saidiencl memberhaving its side port-ions diverging from the stack and being pre-shapedto move said side portions inwardly toward the stack on the applicationof pressure to said end member.

In testimony whereof hereunto aiiix my signature.

WILLIAM EL PRIESS.

